WO2021222844A1

WO2021222844A1 - Optically transparent and thermally conductive polymer based material and method of making the same

Info

Publication number: WO2021222844A1
Application number: PCT/US2021/030316
Authority: WO
Inventors: Nitin Mehra; Kaoru Ueno; Guang Pan; Seyyed Yahya MOUSAVI
Original assignee: Nitto Denko Corporation
Priority date: 2020-04-30
Filing date: 2021-04-30
Publication date: 2021-11-04

Abstract

The present disclosure relates to novel optically transparent thermally conductive films comprising a polymer matrix and an organic sugar alcohol, a dialdehyde, or a combination thereof. Also described herein are adhesive elements and semiconductor constructs comprising the optically transparent thermally conductive films.

Description

OPTICALLY TRANSPARENT AND THERMALLY CONDUCTIVE POLYMER BASED MATERIAL

AND METHOD OF MAKING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 63/017,816, filed April 30, 2020, which is incorporated by reference herein in its entirety.

FIELD

The present disclosure is related to optically transparent thermally conductive composite films for heat dissipation applications and methods for making the same.

BACKGROUND

With an increasing demand forfast and efficient computing, the development of high- performance processors is in great demand. One of the issues plaguing high performance processing is high heat generation. High heat adversely effects the lifetime and performance of newer high-performance processors. Thermal management is an important challenge across server industries including aerospace, electronics, automotive, and the like. Efficient dissipation of heat is required for both reliability and speed of the system. Polymer composites are important candidates for such applications. High thermally conductive fillers have been used to develop thermally conductive polymer-based composites. However, traditional filler-polymer matrix composites have shortcomings including difficulty of fabrication, high-cost, and poor mechanical properties. The majority of thermal conductive polymer-based materials have been based on ceramic, carbon, and/or metallic filler resin combinations, comprising high filler loads up to 80%. High filler loads lead to degradation of mechanical properties (brittle polymer), increased weight, poor optical properties and high cost of fabrication.

Thus, there is a need for novel optically transparent and thermally conductive polymer films that overcome the limitations of films having ceramic, carbon, and/or metallic filler resins. SUMMARY

The present disclosure provides improved thermally conductive transparent composite films and methods for making and using the same.

Some embodiments include a thermally conductive film. The thermally conducting film may comprise a non-electrically conducting polymer having pendant hydroxyl functional groups and/or pendant amino functional groups and a miscible sugar alcohol having at least 4 hydroxyl groups and/or a C3-C7 linear dialdehyde. The polymer and the miscible sugar and/or a C3-C7 linear dialdehyde may be mixed or blended, and may be in a substantial homogeneous mixture, or may be in a single phase. In some embodiments, the non- electrically conductive polymer may comprise a C1-C6 linear polymer subunit. In other embodiments, the non-electrically conducting polymer may comprise a C1-C6 branched polymer subunit. The C1-C6 linear polymer subunit may be, for example, polyvinyl alcohol. The C1-C6 branched polymer subunit may be, for example, carboxymethyl cellulose. In some embodiments, the miscible sugar alcohol is present in a weight% (wt%) of about 1 wt% to about 50 wt% of the total weight of the thermally conductive film. The total weight of thermally conductive film is equal to the sum of the weight of the miscible sugar alcohol and the weight of the non-electrically conductive polymer. In some embodiments, the miscible sugar alcohol may be mannitol. In some examples, the thermally conductive film may further comprise a C3-C8 linear dialdehyde. The C3-C8 linear dialdehyde may be selected from a malondialdehyde, succindialdehyde, glutaraldehyde, or a combination thereof. In some embodiments, the thermally conductive film may further comprise an additional miscible sugar alcohol, wherein the additional miscible sugar alcohol may have at least 4 hydroxyl groups.

Some embodiments include a thermally conductive film wherein the optical transmittance of the thermally conductive film may be 60 % or higher at 550 nm.

Some embodiments include a thermally conductive adhesive element. The thermally conductive adhesive element may comprise a thermally conductive film described herein. In some embodiments, the thermally conductive adhesive element may comprise a pressure sensitive adhesive. Other embodiments may include a semiconductor construct comprising the thermally conductive film described herein.

Some embodiments include a method for making a semiconductor construct comprising the steps of: a) providing a semiconductor subunit and a substrate; and b) applying the thermally conductive films described herein between the semiconductor subunit and the substrate to adhere the semiconductor subunit to the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of thermal bridges formed by organic filler molecules forming hydrogen bonds with the polymer chains.

FIG. 2 is an illustration of 3-dimentional thermal network formed by the hydrogen bonding between sugar alcohol molecules and the polymer.

FIG. 3 is a graphic representation of the % transmittance of some embodiments disclosed herein.

DETAILED DESCRIPTION

The present disclosure includes optically transparent thermally conductive films based on polymers, employing organic fillers in place of carbon, ceramic and metallic fillers. Use of carbon, ceramic and metallic fillers have serious limitations in regard to optical properties of the polymer-filler composite. To address these issues, an alternative approach is presented using an organic filler polymer system. In the present disclosure, an organic filler is incorporated into a bulk polymer, wherein the organic filler interacts with the pendant functional groups of the polymer backbone leading to the development of a thermal network. Bulk polymers are generally considered thermal insulators because they exhibit very poor thermal conductivity. In the bulk state, there is significant chain entanglement which leads to immense heat packet scattering, also known as phonon scattering. As used herein, the term "phonon" or "phonons" refers to heat packets, which are analogous to photons which are energy packets. Intermolecular Interactions and ordering among polymer chains may play a significant role in determining the thermal transport of phonons. Thermal conduction within polymers requires well-defined pathways for the propagation of phonons, and such pathways need to be homogenously distributed across the polymer chain.

Intermolecular interactions, e.g., hydrogen bonding, may impact thermal transport in polymers. The presence of moieties capable of hydrogen bonding, such as hydroxyl groups, may lead to inter/intra hydrogen bonding within the bulk polymer. Bulk polymers lack an efficient thermal network, which leads to a poor thermal conductivity. It is believed that efficient transport of phonons within the polymer is largely responsible for the overall thermal conductivity of polymer-based materials. The efficient conduction of phonons without being scattered may be key to the transfer of heat in non-metal materials. Due to phonon scattering within the polymer chain, thermal conductivity of bulk polymers is on the order of 0.2 W/(m-K), which is considered too low for use in high thermal conductive applications. Incorporating bulk polymers with thermally conductive fillers, and alignment of polymer chains, may lead to efficient thermal transport pathways for developing high thermal conductive materials.

Use of the term "may" or "may be" should be construed as shorthand for "is" or "is not" or, alternatively, "does" or "does not" or "will" or "will not," etc. For example, the statement "the thermally conductive adhesive element may comprise a pressure sensitive adhesive" should be interpreted as, for example, "In some embodiments, the thermally conductive adhesive element comprises a pressure sensitive adhesive," or "In some embodiments, the thermally conductive adhesive element does not comprise a pressure sensitive adhesive."

The present disclosure relates to novel optically transparent thermally conductive films and more specifically to non-electrically conducting polymer-based novel thermally conductive films. In some embodiments, the thermally conductive films of the current disclosure may comprise a non-electrically conducting polymer having pendant hydroxyl functional groups. In other embodiments, the thermally conductive films of the current disclosure may comprise a non-electrically conducting polymer having pendant amino functional groups. In some embodiments, the non-electrically conductive polymer may comprise a C1-C6 linear polymer subunit. In some examples, the polymer subunits may combine to form a semi-crystalline polymer where hydroxyl groups are present at every other carbon alongthe chain. The C₁-C₆ linear polymer subunits are not particularly limited and one skilled in the art would be able to identify which C₁-C₆ linear polymer subunits to utilize in the formation of the non-electrically conducting polymer. Some examples of a C₁-C₆ linear polymer subunit of the non-electrically conducting polymer include, but are not limited to, poly(vinyl pyrrolidone), poly(vinyl amine), poly(ethylene glycol), poly(acrylic acid), poly(vinyl alcohol), or a combination thereof. In some embodiments, the C₁-C₆ linear polymer subunits may be polyvinyl alcohol.

In other embodiments, the non-electrically conducting polymer may comprise a C₁-C₆ branched polymer subunit. Some examples of C₁-C₆ branched polymer subunit of the non- electrically conducting polymer include, but are not limited to, carboxymethyl cellulose, ethyl cellulose, ethyl methyl cellulose, hydroxypropyl cellulose, and hydroxyethyl cellulose. In some embodiments, the C₁-C₆ branched polymer subunit may be, for example, carboxymethyl cellulose. Some embodiments include sodium carboxymethyl cellulose as the C₁-C₆ branched polymer subunit.

In some embodiments, the novel thermally conductive film may comprise a miscible sugar alcohol having at least four (4) hydroxyl groups. The miscible sugar alcohol acts as an organic filler within the thermally conductive film. It is believed that the miscible sugar alcohol organic filler interacts with the non-electrically conductive polymer through hydrogen bonding (e.g., see FIG. 1). It is further believed that these interactions lead to the formation of thermal channels or "thermal bridges" (FIG. 1). It is also believed that sugar alcohols generate efficient 3-dimentional thermal networks through the interaction of the multiple hydroxyl groups present on the sugar alcohol backbone with the pendant hydroxyl groups of the polymer chain. This interaction may be thought of as creating multiple hydrogen bonded thermal bridges with numerous polymer chains (e.g., see FIG. 2). It is believed that these thermal networks play an important role in enhanced thermal conductivity. Some examples of miscible sugar alcohols having at least four (4) hydroxyl groups include, but are not limited to, erythritol, threitol, arabitol, ribitol, xylitol, mannitol, maltitol, sorbital, galactitol, iditol, and volemitol. In some embodiments the miscible sugar alcohol may be mannitol.

The miscible sugar alcohol, such as mannitol, may be present in the amount of about 1 wt% to about 70 wt% of the total weight of the thermally conductive film (the total weight of thermally conductive film = wt of miscible sugar alcohol + wt of PVA). In some embodiments, the amount of the miscible sugar alcohol may be about 2.5-20 wt%, about 10- 15 wt%, about 1-2 wt%, about 2-3 wt%, about 3-4 wt%, about 4-5 wt%, about 5-6 wt%, about 6-7 wt%, about 7-8 wt%, about 8-9 wt%, about 9-10 wt%, about 10-11 wt%, about 11-12 wt%, about 12-13 wt%, about 13-14 wt%, about 14-15 wt%, about 15-16 wt%, about 16-17 wt%, about 17-18 wt%, about 18-19 wt%, about 19-20 wt%, about 20-25 wt%, about 25-30 wt%, about 30-35 wt%, about 35-40 wt%, about 40-45 wt%, about 45-50 wt%, about 1-10 wt%, about 10-20 wt%, about 30-40 wt%, about 40-50 wt%, about 50-60 wt%, about 60-70 wt%, or about 2.5 wt%, about 5 wt%, about 10 wt%, about 20 wt%, about 33 wt%, about 50 wt%, or about any wt% in a range bounded by any of these values, of the total weight of the thermally conductive film.

In some embodiments, the thermally conductive film may further comprise an additional miscible sugar alcohol, wherein the additional miscible sugar alcohol may have at least 4 hydroxyl groups.

The thermally conductive film comprising a non-electrically conducting polymer may further comprise a C3-C8 linear dialdehyde. In some embodiments, the dialdehyde may be used in combination with a miscible sugar alcohol as a crosslinking agent. In some embodiments, the C3-C8 linear dialdehyde may be selected from a malondialdehyde, succindialdehyde, phthalaldehyde, glutaraldehyde, and/or combinations thereof.

Some embodiments include a thermally conductive film comprising non-electrically conducting polymer, further comprising a C3-C8 linear dialdehyde in the absence of a miscible sugar alcohol. In some embodiments, the C3-C8 linear dialdehyde comprises malondialdehyde, succindialdehyde, phthalaldehyde, glutaraldehyde, or a combination thereof.

In some embodiments, the C3-C8 linear dialdehyde, such as glutaraldehyde, may be present in an amount of about 1 wt% to about 40 wt% of the total weight of the non- electrically conducting polymer film and dialdehyde. In other embodiments, the C3-C8 linear dialdehyde may be present in an amount of about 1 wt% to about 40 wt% in addition to miscible sugar alcohol in the non-electrically conducting polymer. In some embodiments, the amount of the C3-C8 linear dialdehyde may be about 2.5-20 wt%, about 20-30 wt%, about 30- 40 wt%, about 10-15 wt, about 1-1.5 wt%, about 1.5-2 wt%, about 2-2.5 wt%, about 2.5-3 wt%, about 3-4 wt%, about 4-5 wt%, about 5-6 wt%, about 6-7 wt%, about 7-8 wt%, about 8- 9 wt%, about 9-10 wt%, about 10-11 wt%, about 11-12 wt%, about 12-13 wt%, about 13-14 wt%, about 14-15 wt%, about 15-16 wt%, about 16-17 wt%, about 17-18 wt%, about 18-19 wt%, about 19-20 wt%, about 20-25 wt%, about 25-30 wt%, about 30-35 wt%, about 35-40 wt%, or about 2.5 wt%, about 5 wt%, about 10 wt%, about 20 wt%, or about any wt% in a range bounded by any of these values, of the total weight of the non-electrically conducting polymer film.

The wt% of a particular organic filler, e.g., sugar alcohol or dialdehyde, is based on the weight of the particular organic filler in relation to the total weight of the particular organic filler and the non-electrically conducting polymer.

In some embodiments, the thermally conductive film may be transparent. As used herein, the term "transparent" describes a film that does not absorb a significant amount of light at 550 nm, allowing for at least 60% of light to pass through so that objects behind the film may be distinctly viewed or recognized when looking through the film. In some embodiments, the thermally conductive film may have transmittance of light from about 60% to about 100%, about 60-65%, about 65-70%, about 70-75%, about 75-80%, about 80-85%, about 85-90%, about 90-95%, about 95-100%, or any transmittance in a range bounded by any of these values.

In some embodiments, the thermally conductive film may be thermally conductive. Some embodiments include a thermally conductive film with a thermal conductance greater than about 0.42 l (Wm ^_1K ^_1). In some embodiments, the thermal conductance is greaterthan about 0.43 l, about 0.44 l, about 0.45 l, about 0.46 l, about 0.47 l, about 0.48 l, about 0.49 l, about 0.50 l, about 0.51 l, about 0.52 l, about 0.53 l, about 0.54 l, about 0.55 l, about 0.56 l, about 0.57 l, about 0.58 l, about 0.59 l, about 0.60 l, or about 0.61 l. In some embodiments, the thermal conductance is up to about 0.5 l, about 0.6 l, about 0.7 l, about 0.9 l about 1 l, or about 2 l. Some embodiments include a thermally conductive adhesive element. The thermally conductive adhesive element may comprise a thermally conductive film described herein. In some embodiments, the thermally conductive adhesive element may comprise a pressure sensitive adhesive. Some embodiments include a pressure sensitive adhesive comprising a thermally conductive film disposed on a carrier layer. The carrier layer is not particularly limited, and any suitable carrier layer may be used. In some embodiments, the carrier layer may be selected from any suitable substrate for structural support in adhesive films. In some embodiments, the carrier may comprise non-woven materials, woven materials, or a woven substrate. In some embodiments, the woven substrate may comprise silica (glass), aramid, carbon fiber, metal oxides, minerals, ceramic, or other fine diameter, synthetic, man-made fibers. In some embodiments, the non-woven materials may comprise cellulose, rayon, cloth, polyamide fluoride (PVDF), polyethylene (PE), polyethylene terephthalate (PET), polyether ether ketone (PEEK), and/or mixtures thereof.

In some examples, the surface of the carrier layer substrate may be subject to a coating treatment with a primer so as to have an improved adhesion to the thermally conductive adhesive film. Examples of treatments include corona treatment, chromic acid treatment, exposure to ozone, exposure to flame, and exposure to oxidation treatment through a chemical or physical process, such as treatment with ionizing radiation.

In some embodiments, the thermally conductive adhesive element may comprise a release liner coated on and in physical contact with a surface of the thermally conductive film layer. The release liners in the present disclosure are not particularly limited, and any suitable release liner may be employed. In some embodiments, the release liner may be detached from the adhesive before adherence to the surfaces to be bonded together. In some embodiments, the release liner may comprise any suitable material, such as a polyolefin (e.g., polyethylene, polyethylene terephthalate, polypropylene), a silicone or a fluoropolymeric material. In some embodiments, release liners may be generic materials (e.g., polymers, cellulose, paper, etc.) that are coated with non-stick materials, such as silicone, to make them releasable, such as siliconized paper.

In some embodiments, the release liner may be a member which includes a liner base and a release layer (releasing coating film). In some embodiments, the release layer is disposed on the adhesive layer so that the release layer faces the adhesive layer. The release layer may be formed from, for example, a silicone-based release agent. Examples of silicone- based release agents include thermosetting silicone-based release agents and silicone-based release agents curable with ionizing radiation. Material usable for forming the release layer are not limited to silicone-based release agents, and any suitable material may be selected in accordance with the type of adhesive constituting the adhesive layer. Although the thickness of the release liner may be of any suitable pre-determined value, in some embodiments the thickness thereof may be a value in the range of 10 pm to about 200 pm.

Some embodiments may include a semiconductor construct. In some embodiments, the semiconductor construct may comprise the thermally conductive film described herein.

Some embodiments include a method for making a semiconductor construct, comprising: a) providing a semiconductor subunit and a substrate; and b) applying a thermally conductive film described herein between the semiconductor subunit and the substrate to adhere the semiconductor subunit to the substrate. In some embodiments, the thermally conductive film may comprise a non-electrically conducting polymer as described herein. In other embodiments, the thermally conductive film may comprise a miscible sugar alcohol comprising at least four (4) hydroxyl functional groups.

EMBODIMENTS

Embodiment 1. A thermally conductive film comprising: a non-electrically conducting polymer having hydroxyl functional groups; and a miscible sugar alcohol having at least 4 hydroxy groups.

Embodiment 2. The thermally conductive film of embodiment 1, wherein the non- electrically conducting polymer comprises a C₁-C₆ linear polymer subunit or C₁-C₆ branched polymer subunit.

Embodiment s. The thermally conductive film of embodiment 1, wherein the non- electrically conducting polymer may be polyvinyl alcohol.

Embodiment 4. The thermally conductive film of embodiment 1, wherein the non- electrically conducting polymer may be carboxymethyl cellulose.

Embodiment 5. The thermally conductive film of embodiment 1, wherein the miscible sugar alcohol may be mannitol. Embodiment 6. The thermally conductive film of embodiment 1, wherein the miscible sugar alcohol has a wt% of the total weight of the thermally conductive film between 2.5 wt% and 20 wt%.

Embodiment 7. The thermally conductive film of embodiment 1, further comprising a C3-C7 linear dialdehyde.

Embodiment s. The thermally conductive film of embodiment 7, wherein the C3-C7 dialdehyde is selected form malondialdehyde, succindialdehyde, and/or glutaraldehyde. Embodiment 9. The thermally conductive film of embodiment 1, further comprising at least one additional sugar alcohol having at least 4 hydroxy groups or combination thereof. Embodiment 10. The thermally conductive film of embodiment 1, wherein the optical transmittance of the thermally conductive film is at least 60% at 550nm.

Embodiment 11. A thermally conductive adhesive element comprising the thermally conductive film of embodiments, 1, 2, 3, 4, 5, 6, 1 , 8, 9, or 10.

Embodiment 12. The thermally conductive adhesive of embodiment 11, further comprising a pressure sensitive adhesive.

Embodiment 13. A semiconductor construct comprising the thermally conductive adhesive of embodiments 11 and 12.

Embodiment 14. A method for making a semiconductor construct comprising the steps of; a. Providing a semiconductor subunit and a substrate; and b. Applying the thermally conductive film of embodiments 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 between the semiconductor of subunit and substrate to adhere the semiconductor subunit. Embodiment 15. The method of embodiment 14, wherein the thermally conductive film comprises a non-electrically conducting polymer.

Embodiment 16. The method of embodiment 14, wherein the thermally conductive film comprises a sugar alcohol comprising at least 4 hydroxyl functional groups.

EXAMPLES

Example 1 Preparation of Thermally Conductive Film

Example 1.1 CE-1: To a flask filled with 92 mL of Milli-Q-water (MilliporeSigma, Burlington, MA, USA) was added 8 g of poly(vinyl alcohol) (PVA) (MilliporeSigma). The solution was stirred on a heated magnetic stir plate at 85 °C for 2 hours, until the solution became transparent. After the 2 hours the clear solution was then poured into petri dishes and dried in an oven at 55 °Cfor 1-2 days to achieve a free-standing film. Samples where then used without further purification. For TCFl-TFC-11 the samples were made in the same manner except mannitol or glutaraldehyde was added according to the amounts listed in Table 1 after obtaining transparent PVA solution. For example, TCF-l-TCF-3, the appropriate amount of mannitol was added to transparent PVA solution and mixture was allowed to stir for 3 hours at 60 °C. For TCF-4-TCF-7 the appropriate amount of mannitol was added to transparent PVA solution, and the solution was allowed to stir for 5 minutes at 60 °C, then the appropriate amount of glutaraldehyde was added, and the solution mixture was then stirred for 2 hours at 60 °C.

Example 1.2 CE-2: To a flask filled with 100 mL of Milli-Q-water (MilliporeSigma, Burlington, MA, USA) was added 1.64 g of sodium carboxymethyl cellulose (SCMC) (MilliporeSigma). The solution was stirred on a heated magnetic stir plate at 55 °C for 1 hour, until the solution became transparent. After 1 hour, the clear solution was then poured into petri dishes and dried in an oven at 55 °Cfor 1-2 days to achieve a free-standing film. Samples where then used without further purification. For TCF12-TFC-13, mannitol was added gradually after the SCMC solution became transparent and further mixed mechanically for 1 hour at 55 °C. Then similar process was followed, clear solution was poured into petri dishes and dried in an oven at 55 °C for 1-2 days to achieve a free-standing film.

Example 2: Measurement of thermal conductivity (l) of the composites: The thermal conductivity was determined by following equation: l [Wm ^_1K ^_1] = a [mm²s ^_1] x p [gem ³] x C_p [J K ^_1g ^_1] where a, p and C_p are thermal diffusivity, specific density and specific heat capacity, respectively. Thermal diffusivity was determined with a flash analyzer (LFA-467, Netzsch). For specific density, samples (thickness 100-250 micron) was cut using an 8 mm diameter punch and weight was determined using a micro balance (Mettler Toledo precision balance) and accordingly specific density was calculated using volume and weight. C_p was determined by a differential scanning calorimetry (DSC 2500, TA instrument). The measured thermal conductivity is summarized in Table 1.

Example 3: Measurement of optical transmittance: Optical transparency is measured using UV-3600 (UV-VIS-NIR Spectrophotometer, Shimadzu). Film with size greater than 2- inch X 2-inch were used for the measurement. % Transmittance was read from 350 nm to 700nm; % Transmittance at 550 nm is used for film characterization. FIG. 3 displays the data for examples TCF-l-TCF-3 and TCF-12 and TCF-13.

Table 1.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties, such as, molecular weight, reaction conditions, and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached embodiments are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents. To the scope of the embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. For the processes and/or methods disclosed, the functions performed in the processes and methods may be implemented in differing order, as may be indicated by context. Furthermore, the outlined steps and operations are only provided as examples and some of the steps and operations may be optional, combined into fewer steps and operations, or expanded into additional steps and operations.

This disclosure may sometimes illustrate different components contained within, or connected with, different other components. Such depicted architectures are merely exemplary, and many other architectures may be implemented which achieve the same or similar functionality.

The terms used in this disclosure and in the appended embodiments, (e.g., bodies of the appended embodiments) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes, but not limited to," etc.). In addition, if a specific number of elements is introduced, this may be interpreted to mean at least the recited number, as may be indicated by context (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations of two or more recitations). As used in this disclosure, any disjunctive word and/or phrase presenting two or more alternative terms should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phase "A or B": will be understood to include the possibilities of "A" or "B" or "A and B."

The terms "a," "an," "the" and similar referents used in the context of describing the present disclosure (especially in the context of the following embodiments) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of any and all examples, or representative language (e.g., "such as") provided herein is intended merely to better illuminate the present disclosure and does not pose a limitation on the scope of any embodiments. No language in the specification should be construed as indicating any non-embodied element essential to the practice of the present disclosure.

Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and embodied individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended embodiments.

Certain embodiments are described herein, including the best mode known to the inventors for carrying out the present disclosure. Of course, variations on these described embodiments, will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the present disclosure to be practiced otherwise than specifically described herein. Accordingly, the embodiments include all modifications and equivalents of the subject matter recited in the embodiments as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context. In closing, it is to be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments. Other modifications that may be employed are within the scope of the embodiments. Thus, by way of example, but not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the embodiments are not limited to the embodiments precisely as shown and described.

Claims

CLAIMS What is claimed is:

1. A thermally conductive film comprising: a non-electrically conducting polymer having pendant hydroxyl functional groups; and a miscible sugar alcohol having at least 4 hydroxy groups, a C₃-C₇ linear dialdehyde, or a combination thereof.

2. The thermally conductive film of claim 1, wherein the non-electrically conducting polymer comprises a C1-C6 linear polymer subunit or a C1-C6 branched polymer subunit.

3. The thermally conductive film of claim 1 or 2, wherein the non-electrically conducting polymer comprises polyvinyl alcohol.

4. The thermally conductive film of claim 1, 2, or 3, wherein the non-electrically conducting polymer comprises carboxymethyl cellulose.

5. The thermally conductive film of claim 1, 2, 3, or 4, comprising the miscible sugar alcohol.

6. The thermally conductive film of claim 1, 2, 3, 4, or 5, wherein the miscible sugar alcohol comprises mannitol.

7. The thermally conductive film of claim 5 or 6, wherein the miscible sugar alcohol is about 1 wt% to about 50 wt% of the total weight of the thermally conductive film.

8. The thermally conductive film of claim 1, 2, 3, 4, 5, or 6, comprising the C₃-C₇ linear dialdehyde.

9. The thermally conductive film of claim 8, wherein the C3-C7 linear dialdehyde comprises malondialdehyde.

10. The thermally conductive film of claim 8 or 9, wherein the C3-C7 linear dialdehyde comprises succindialdehyde.

11. The thermally conductive film of claim 8, 9, or 10, wherein the C3-C7 dialdehyde comprises glutaraldehyde.

12. The thermally conductive film of claim 8, 9, 10, or 11, wherein the C3-C7 linear dialdehyde is about 2.5 wt% to about 20 wt% of the total weight of the thermally conductive film.

13. The thermally conductive film of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the optical transmittance of the thermally conductive film is at least 60% at 550 nm.

14. A thermally conductive adhesive element comprising the thermally conductive film of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13.

15. The thermally conductive adhesive of claim 14, further comprising a pressure sensitive adhesive.

16. A semiconductor construct comprising the thermally conductive adhesive of claim 14 or 15.

17. A method for making a semiconductor construct, comprising: applying the thermally conductive film of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 between a semiconductor subunit and a substrate, to adhere the semiconductor subunit to the substrate.